To date, a variety of beta-lactam drugs have been developed and beta-lactam drugs have become clinically extremely important antimicrobial drugs. However, there are increasing number of bacterial types which have obtained resistance against beta-lactam drugs by producing beta-lactamase, which degrade beta-lactam drugs.
According to the Ambler molecular classification, beta-lactamases are largely classified into four classes. Specifically, these are Class A (TEM type, SHV type, CTX-M type, KPC type and the like), Class B (IMP type, VIM type, L-1 type and the like), Class C (AmpC type) and Class D (OXA type and the like). Amongst these, Classes A, C and D types are largely classified into serine-beta-lactamase, on the other hand, Class B type is classified into metallo-beta-lactamase. It has been known that both have respectively different mechanisms to each other in terms of hydrolysis of beta-lactam drugs.
Recently, clinical problem has been occurring due to the existence of Gram negative bacteria which have become highly resistant to a number of beta-lactam drugs including Cephems and Carbapenems by producing Class A (ESBL) and D types serine-beta-lactamases which have an extended substrate spectrum, and Class B type metallo-beta-lactamase which have an extended substrate spectrum. Particularly, metallo-beta-lactamase is known to be one of the causes of obtaining multidrug-resistance in Gram negative bacteria. Cephem compounds which exhibit intermediate activity against metallo-beta-lactamase producing Gram negative bacteria are known (e.g., Patent Document 1 and Non-Patent Document 1). However, there is a demand for development of Cephem compounds which exhibit more potent antimicrobial activity, in particular more effective against a variety of beta-lactamase producing Gram negative bacteria.
One of the known antimicrobials having high anti-Gram negative bactericidal activity is Cephem compounds having a catechol group intramolecularly (e.g., Non-patent Documents 2-4). The action thereof is that the catechol group forms a chelate with Fe3+, thereby the compound is efficiently incorporated into the bacterial body through the Fe3+ transportation system on the cellular membrane (tonB-dependent iron transport system). Therefore, research has been conducted on compounds having catechol or similar structure thereto, on the 3-side chain or 7-side chain moiety on the Cephem backbone.
Patent Documents 2-8 and Non-patent Document 5 describe compounds having a partial structure of the 7-side chain and a quaternary salt structure on the Cephem backbone. However, these documents merely describe a pyridinium structure, and merely disclose compounds having a formamide group at the 7-position in most cases. Furthermore, for example, most compounds disclosed in Patent Document 2 have a penicillin structure.
Non-patent document 1 and Patent Documents 8-12 and 15 describe catechol type derivatives having a catechol group on the 3-side chain moiety on the Cephem backbone. Patent Documents 10, 11, 13, and 14 describe pseudo-catechol type derivatives having a hydroxypyridone group on the 3-side chain moiety on the Cephem backbone. Patent Documents 16 and 17 disclose Cephem compounds having a quaternary ammonium group.
Moreover, in the above documents, which describe Cephem compounds having a catechol group in their structure, there is no description of Class B type metallo-beta-lactamase, and specific antimicrobial activity against a wide variety of Gram negative bacteria including Class B type.
Patent Document 22 discloses a compound having S-pyridinium on the 3-side chain of the Cephem backbone. However, this document does not disclose a compound having a bioisoster of carboxyl ion, such as tetrazoryl, on the 4-side chain of the Cephem backbone.
Additionally, Patent Document 7 describes that penicilin compounds having a tetrazolyl group at position 3 of the penicilin skeleton has superior stability against beta-lactamase. However, a Cephem compound having a tetrazolyl group at position 4 of the penicilin skeleton is not disclosed in this document.
Patent Documents 18, 19, 20 and Non-Patent Document 6 describe Cephem compounds having a tetrazolyl group at position 4 of the penicilin skeleton. However, a compound having a quaternary ammonium group at the 3-side chain is not disclosed in these documents.
On the other hand, Cephem compounds having catechol type substituents is disclosed by the present applicant (Patent Document 21). Furthermore, the present applicant has already disclosed an application relating to Cephem antimicrobial agent having potent antimicrobial activity against beta-lactamase producing Gram negative bacteria (Patent Documents 23-25). However, these documents do not disclose a compound having S-pyridinium at position 3 of the cephem skeleton.